1. Field of the Invention
This invention relates generally to magnetic levitation rail systems, and more particularly to a rail system based on a compact magnetic levitation car which can travel in an evacuated tube of minimal radial dimensions while allowing passenger comfort consistent with automobiles.
2. Brief Description of the Prior Art
Magnetic levitation vehicles and railways have been a practical reality for over a decade, and, for all the potential maglev transportation holds, the application of maglev trains has not gone past a few limited tracks which do little more than prove maglev systems work. An optimistic estimate for the maximum economical speed for a maglev train which is exposed to atmospheric pressure is approximately 570 mph. Compared to the 190 mph velocity of the fastest conventional train systems in France, the maglev train's velocity is approximately three times faster. This three-fold increase is at the expense of building a totally new and extremely expensive rail system. This additional speed simply has not proven to be enough incentive to warrant the capital expenditures which are necessary to replace existing train routes and compete with air travel.
The present invention entails major modifications to existing magnetic levitation vehicles with the goal of reducing implementation costs and expanding capabilities of the rail system. By basing a maglev rail system around a smaller maglev "car" rather than a maglev "train" , the economics of using evacuated tubes to isolate the rail system from air resistance is greatly improved, and the capabilities of the rail system are expanded to include many aspects of transportation which are presently only feasible with private vehicles.
Minovitch, U.S. Pat. Nos. 3,954,064 and 4,075,948, discloses a train system which is operated in evacuated tunnels. Minovitch's invention takes advantage of the reduced energy losses of an evacuated railway system and has great fuel economy, but the system is based around a rather large and bulky train which is very expensive to build. Minovitch's system is based on gravitational energy and basic concepts of magnetic levitation and travel in evacuated environments. The present invention uses the reduced energy loss environment of evacuated tubes, but is much less expensive to build and is more like an automobile than a train. The present invention is based around maglev cars which can travel in much smaller tubes than the tunnels described in the above patents. These tubes cost less to construct than a lane of a highway, and the rail system in these tubes allows travel velocities greater than any jet aircraft.
Hirtz, U.S. Pat. No. 4,881,469 discloses a train system based on travel in tubes; however, Hirtz's system is based on complex switching methods involving moving rail and tube wall sections. The present invention does not rely on moving parts for switching and, beyond basic concepts of magnetic levitation, is not similar.
Pougue, U.S. Pat. No. 3,763,788 discloses a system for switching a high speed captive surface vehicle from a primary guideway to a secondary guideway by magnetic attraction. Pougue operates in a different manner than the present invention. Pougue utilizes laterally extending magnetic elements to exert lateral forces for guidance while upper monorail type magnetic elements provide attractive suspension. The present invention uses laterally extending magnetic elements which primarily exert vertical suspension forces. The laterally extending magnetic elements of the present invention can also be configured for attractive or repulsive suspension forces. Furthermore, as a source of suspension, the laterally extending magnetic elements of the present invention must provide continuous interactions on both sides of the vehicle. Pougue's system will allow suspension with either or both lateral rails being absent.
Breitling, U.S. Pat. No. 3,964,398, describes a switching system for maglev trains. This system is specific to trains where the suspension magnets are located at the bottom of the vehicle and may have significant distances without magnetic suspension interactions during the high radius corners required at high speed velocities. Also, embankment on the corner will interfere with the operation of Breitling's design.
Yamamura et al., U.S. Pat. No. 4,646,651, describes a method of stabilizing a maglev train. The magnet-rail configuration described in Yamamura's patent is effective, but is more sophisticated and expensive than is required to create the stability for the vehicles of the present invention.
Vinson, U.S. Pat. No. 4,307,668, and van der Heide, U.S. Pat. No. 4,356,772, describe methods of magnetic levitation. Each inventor applies his unique modification to improve magnetic levitation as prescribed by different goals and criteria.
Lichtenberg, U.S. Pat. No. 3,847,087 discloses a non-contact means of transferring electrical energy to be used by the vehicle.
Isolation of vehicle and passenger movements are described by Yamashita, U.S. Pat. No. 4,273,054, and Feistkorn, U.S. Pat. No. 4,259,908.
Steinmetz, U.S. Pat. No. 4,763,578 discloses methods of eliminating the propagation of vibrations due to levitation control methods at low velocities. Steinmetz's methods find applications in feedback-control methods of attractive levitation, whereas the present invention finds applications in repulsive levitation. In repulsive levitation, the changes in magnetic flux in rail elements at low travel velocities are not sufficient to induce the repulsive forces necessary to sustain levitation.
All the above mentioned patents are directed toward a "train" levitated by magnetic interactions and, in the case of Minovitch's patent, around the reduced air friction of an evacuated environment. Comparing a maglev "train" to the present maglev "car" is like comparing a bus to an automobile. It is important to note that the present invention is not merely a reduction in size. Accordingly, many of the switching and guidance systems which work well for a maglev "train" designed for velocities less than 570 mph are not appropriate for the present maglev "car" which operates at higher velocities and has different design criteria.
The present invention is distinguished over the prior art in general, and these patents in particular by a system utilizing a compact magnetic levitation vehicle which provides passenger comfort consistent with automobiles and travels suspended on ferromagnetic rails in evacuated tubes of minimal radial dimension extending between vehicle loading and unloading stations or at atmospheric conditions. A pair of guides extend outwardly along opposite sides of the vehicle and contain magnetic elements. Electrically conductive, ferromagnetic, magnetic, or electromagnetic sections in the rails correspond to the magnetic elements in the vehicle guides. Linear motors or controlled interaction with rail members provide propulsion an braking. Extensive portions of the evacuated tubes are provided with two sets of rails, one set of rails functionally located above the other. Rail switching is accomplished by selectively interacting with alternative levitation rails which are located at switching locations. Tube evacuation may be supplemented by vacuum pumps on the vehicle to draw in air during travel. The vehicle may have turbines which draw in air and exhaust compressed gases into cylinders.
The present invention places emphasis on repulsive levitation because repulsive levitation (1) provides stable levitation without feedback type of control methods, (2) has magnetic drag forces which decrease with increasing velocity, and (3) has increased levitation heights which decrease rail construction costs. The present system is also inherently safe from derailment since (1) the guides will be physically supported by the rails if levitation is lost, (2) the slope of the rail provides stable lateral control during levitation, and (3) the wall of the tube prevents lateral derailment of the vehicle.